WO1997023333A1 - Compositions a base d'amidon - Google Patents

Compositions a base d'amidon Download PDF

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Publication number
WO1997023333A1
WO1997023333A1 PCT/US1996/020116 US9620116W WO9723333A1 WO 1997023333 A1 WO1997023333 A1 WO 1997023333A1 US 9620116 W US9620116 W US 9620116W WO 9723333 A1 WO9723333 A1 WO 9723333A1
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WO
WIPO (PCT)
Prior art keywords
starch
based composition
ofthe
range
fibers
Prior art date
Application number
PCT/US1996/020116
Other languages
English (en)
Inventor
Per J. Andersen
Simon K. Hodson
Original Assignee
E. Khashoggi Industries
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by E. Khashoggi Industries filed Critical E. Khashoggi Industries
Priority to AU14243/97A priority Critical patent/AU1424397A/en
Publication of WO1997023333A1 publication Critical patent/WO1997023333A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
    • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
    • B27N3/002—Manufacture of substantially flat articles, e.g. boards, from particles or fibres characterised by the type of binder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
    • B27N3/00—Manufacture of substantially flat articles, e.g. boards, from particles or fibres
    • B27N3/007—Manufacture of substantially flat articles, e.g. boards, from particles or fibres and at least partly composed of recycled material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/003—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor characterised by the choice of material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/04—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles using movable moulds
    • B29C43/06—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles using movable moulds continuously movable in one direction, e.g. mounted on chains, belts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/02—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles
    • B29C44/04—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities
    • B29C44/0407—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of definite length, i.e. discrete articles consisting of at least two parts of chemically or physically different materials, e.g. having different densities by regulating the temperature of the mould or parts thereof, e.g. cold mould walls inhibiting foaming of an outer layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
    • B29C67/20—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 for porous or cellular articles, e.g. of foam plastics, coarse-pored
    • B29C67/202—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 for porous or cellular articles, e.g. of foam plastics, coarse-pored comprising elimination of a solid or a liquid ingredient
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00
    • B29C67/24—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00 characterised by the choice of material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D43/00—Lids or covers for rigid or semi-rigid containers
    • B65D43/14—Non-removable lids or covers
    • B65D43/16—Non-removable lids or covers hinged for upward or downward movement
    • B65D43/162—Non-removable lids or covers hinged for upward or downward movement the container, the lid and the hinge being made of one piece
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
    • B65D65/38—Packaging materials of special type or form
    • B65D65/46—Applications of disintegrable, dissolvable or edible materials
    • B65D65/466—Bio- or photodegradable packaging materials
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
    • C08L3/02—Starch; Degradation products thereof, e.g. dextrin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/10—Moulds or cores; Details thereof or accessories therefor with incorporated venting means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C43/00—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor
    • B29C43/02—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles
    • B29C43/04—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles using movable moulds
    • B29C43/06—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles using movable moulds continuously movable in one direction, e.g. mounted on chains, belts
    • B29C43/08—Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor of articles of definite length, i.e. discrete articles using movable moulds continuously movable in one direction, e.g. mounted on chains, belts with circular movement, e.g. mounted on rolls, turntables
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2003/00—Use of starch or derivatives as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0037—Other properties
    • B29K2995/0059—Degradable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/712—Containers; Packaging elements or accessories, Packages
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05D—HINGES OR SUSPENSION DEVICES FOR DOORS, WINDOWS OR WINGS
    • E05D1/00—Pinless hinges; Substitutes for hinges
    • E05D1/02—Pinless hinges; Substitutes for hinges made of one piece
    • E—FIXED CONSTRUCTIONS
    • E05—LOCKS; KEYS; WINDOW OR DOOR FITTINGS; SAFES
    • E05Y—INDEXING SCHEME RELATING TO HINGES OR OTHER SUSPENSION DEVICES FOR DOORS, WINDOWS OR WINGS AND DEVICES FOR MOVING WINGS INTO OPEN OR CLOSED POSITION, CHECKS FOR WINGS AND WING FITTINGS NOT OTHERWISE PROVIDED FOR, CONCERNED WITH THE FUNCTIONING OF THE WING
    • E05Y2900/00—Application of doors, windows, wings or fittings thereof
    • E05Y2900/60—Application of doors, windows, wings or fittings thereof for other use
    • E05Y2900/602—Application of doors, windows, wings or fittings thereof for other use for containers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
    • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Definitions

  • the present invention relates to the manufacture of starch-bound articles having a cellular structural matrix formed by removing water by evaporation from a starch-based composition. More particularly, the present invention involves novel compositions and methods which greatly improve the reliability ofthe thermal formation process used to manufacture the starch-bound articles.
  • the improved compositions and methods ofthe present invention allow for much greater efficiency and variability in the operating variables, such as fill weight, mold temperature, water concentration, vent hole size, and the like, while obtaining a final molded article having superior strength and other physical characteristics.
  • Another, less successful method involves melting and then cooling the starch like a thermoplastic material to form a solidified material.
  • a starch-containing mixture is typically shaped into an appropriate article between heated molds for a period of time sufficient to first gelate the starch-based binder and then remove a substantial portion ofthe water by evaporation to form a solidified or semi-hardened material.
  • the molded starch- bound articles formed by gelation can have a wide range of densities and strength properties. Because such articles are largely starch-bound, they are readily biodegradable.
  • the products are generally brittle and require either the addition of a synthetic polymer or a time-consuming "conditioning step" followed by a coating step in order to establish and then maintain the proper moisture content in order to impart strength, toughness, and flexibility to the articles. They require relatively high concentrations of starch and low concentrations of water, which results in relatively long molding times, relatively high minimum mass and thickness requirements, and expensive equipment and admixtures in order to improve the quality ofthe molded articles.
  • Another problem is that many of the molding conditions, such as fill weight, molding time, water content, and the like, must be maintained within a very small operating "window” with hardly any variation in order to successfully mold a product that is fully formed, does not collapse, and/or which does not have excessive "streaming" (fissures or cracks) or other physical flaws arising from improper flow while filling the mold cavity, all of which greatly reduce the physical strength and performance of the molded article.
  • the manufacture of starch-based articles by gelation has heretofore typically been far more expensive than simply making articles from conventional thermoplastics.
  • the processing conditions necessary to form an adequate product it is known, for example, that increasing the total water in the form of fill weight or water concentration, or the rate at which the water reacts in the form of vent hole size or mold temperature, each increase the "reactivity" ofthe starch-based composition and molding system.
  • the "reactivity" of the molding system is defined as the rate of water vapor formation, the rate of expansion ofthe starch-based composition within the heated mold, the rate and extent of expulsion ofthe composition from the mold, and the rate of escape of water vapor from the system. It is also related to the magnitude of internal pressure that builds up within the mold as a result ofthe formation of steam. It is conventionally believed that increasing the reactivity ofthe molding system generally leads to decreased success in forming an adequate product.
  • the reactivity ofthe composition and molding process are typically made most efficient by minimizing the amount of water that is included within the starch-based composition.
  • certain relationships exist between water concentration and vent hole size, mold temperature, article wall thickness, viscosity, and baking time.
  • an increase in the water concentration ofthe molding composition results in lower viscosity and requires a decrease in vent hole size and baking time and an increase in part thickness and mold temperature in order to maintain the operating window and form an acceptable part.
  • An increase in vent hole size results in a decrease in baking time but requires a decrease in the water concentration and/or an increase in part thickness, viscosity, and mold temperature in order to form an acceptable part.
  • An increase in mold temperature results in decreased baking time but requires an increase in vent hole size, part thickness, and/or water concentration to achieve the requisite decreased viscosity ofthe molding composition. In order to decrease baking time, it is necessary to increase the vent hole size and mold temperature and to reduce the water concentration, and/or the part thickness.
  • pregelatinized starch or other thickening agents that have been added to the starch-based compositions are typically minimized in order to obtain a composition that is sufficiently flowable and moldable.
  • gelatinized starch or other thickening agents such as cellulosic ethers or gums greatly increase the viscosity ofthe composition, their use generally requires the addition of more water in order to overcome the viscosity-increasing effect of the thickening agent.
  • unmodified starch granules do not appreciably affect the viscosity of the fluid fraction of the molding mixture.
  • the balance of components besides the starch comprises predominantly water.
  • Other components that have been used in relatively minor amounts include a mold release agent, dyes, organic and inorganic fillers, and fibrous materials.
  • the fibrous component is typically included in very small amounts or excluded altogether. If included at all, the fibrous component within prior art compositions typically has a low fiber length ( ⁇ 1.5 mm) and/or a low aspect ratio ( ⁇ 10:1).
  • the fibrous component is simply a fibrous particulate filler, such as bran or sawdust.
  • compositions and methods for improving the dispersion of fibers or other fillers within starch-based materials without the need for using highly aqueous slurries with intolerably high reactivity, such as slurries used in the paper-making industry. It would yet be a significant improvement if such compositions and methods allowed for a more thorough dispersion of fibers, particularly relatively long-length fibers (i.e., those having an average length greater than about 2 mm) and/or fibers of high aspect ratio (i.e., at least about 25:1), within the starch-based compositions.
  • compositions and methods that allowed for the inclusion of higher concentrations of inorganic fillers while maintaining adequately strong molded starch-bound articles.
  • compositions and methods that made possible the manufacture of articles while increasing the operating window of allowable water concentrations, fill weights, molding temperatures, and vent sizes during formation ofthe articles.
  • compositions and methods resulted in the ability to significantly reduce the thermal molding time while manufacturing articles that are of equal or greater quality compared to articles manufactured using the compositions and methods of the prior art. It would be a further improvement in the art if such compositions and methods yielded hardened, starch-bound articles that do not require the addition of synthetic polymers or prolonged, high-humidity conditioning in order to obtain the required flexibility, strength and toughness.
  • compositions and methods that yielded starch-bound articles that did not require the application of a coating or the inclusion of a synthetic polymer to maintain the proper moisture within the starch- bound articles.
  • Such starch-based compositions as well as methods for manufacturing articles having a starch-bound cellular matrix from such compositions, are disclosed herein.
  • the present invention relates to compositions and methods which improve the manufacturing process used to manufacture shaped articles from starch-based compositions, particularly those involving the use of heated molding apparatus. It has been found that, contrary to the conventional wisdom, by significantly increasing the concentration of pregelatinized starch relative to the concentration of the ungelatinized starch component, it is possible to greatly increase the range or "window" of allowable processing conditions required to form an adequate product. The increased reactivity that naturally follows from, e.g., increasing the water concentration within the molding composition, the fill weight, the mold temperature, and/or vent hole size, is moderated by including significant amounts of pregelatinized starch within the molding composition.
  • Starch-bound articles having a foamed cellular matrix have been conventionally manufactured as follows.
  • the composition typically includes a large quantity of ungelatinized starch, such as unmodified starch granules derived from potatoes or corn.
  • starch granules do not appreciably increase the viscosity ofthe composition but act as solid particulate fillers as long as the molding composition is kept below the gelation temperature of the starch granules.
  • the gelation temperature of starch granules is between about 65° C to about 95° C, depending on the type of starch granules involved.
  • the molding composition is placed between heated molds corresponding to a desired shape of the final molded article. Upon closing the male and female molds around the composition, the composition is quickly heated to above the boiling point of water, which is also typically above the gelation temperature of the unmodified starch granules. This causes the gelation ofthe starch granules and subsequent removal of water by evaporation.
  • the gelatinized starch hardens into a fairly strong binding matrix upon the evaporative removal of a substantial quantity of the water.
  • the higher quantity of water within the mixture the higher the reactivity and the more porous and lightweight will be the final molded article due to the formation of a greater volume of voids due to the removal of the larger amount of water.
  • the heated molds that are used to manufacture the starch-bound articles typically include a plurality of vent holes located near the top ofthe molding apparatus through which the excess composition and pressurized water vapor can escape from the molds. Excess composition that is emitted out of the vent holes typically hardens around the edge ofthe molded article as "flashing", which must subsequently be removed by means of a blade or other flashing removal device.
  • the inclusion of significant quantities of well-dispersed fibers within the starch- based compositions of the present invention aids in the formation of articles having greatly reduced wall thickness and greatly increased strength.
  • the fibers allow for the demolding of molded articles in which a significant quantity of residual water can be retained without collapse of the article wall or destruction of the cellular matrix, which usually occurs when an article having little or no fibers is demolded.
  • a completely dried article having little or no fibers is initially very brittle and weak and must be subjected to prolonged conditioning in a high humidity environment in order to reduce the brittleness and increase the flexibility, ductility and strength ofthe article.
  • fibers also allows for the inclusion of far greater amounts of inorganic filler materials, such as calcium carbonate, mica, clay, and the like, because the fibers are able to offset the loss of strength that generally occurs as a result of adding non- reinforcing fillers.
  • Filler materials will usually constitute by far the least expensive component within the starch-based composition, which decreases the cost of the starch- based compositions.
  • compositions that include appreciable quantities of inorganic filler materials also yield a molded product that can withstand greater variations in ambient moisture. For example, it is known that articles manufactured from compositions that include mostly starch and water are quite sensitive to variations in ambient moisture.
  • the general practice for obtaining good fiber dispersion without unduly increasing the reactivity ofthe molding system has been to use only that amount of pregelatinized starch necessary to adequately disperse the fibers.
  • a further increase in the concentration of pregelatinized starch did not at first appear to provide any increased benefit since the only purpose of pregelatinizing a portion of the starch was to facilitate fiber dispersion.
  • Any pregelatinized starch above the minimum amount necessary to adequately disperse the fibers was thought to simply require more water in order to maintain an adequately moldable composition and, in turn, increase the reactivity of the system in a negative manner.
  • pregelatinized starch Although small amounts of pregelatinized starch ( ⁇ 10% by weight of overall starch) do not appreciably offset the increased reactivity caused by increases in water concentration, the use of about 12% or more by weight of pregelatinized starch allows for the inclusion of larger and more variable amounts of water, while still being able to mold a high quality article.
  • pregelatinized starch also increases the range or window of acceptable fill weights of starch-based composition that can be placed into the mold.
  • the dynamics involved in the molding of foamed starch-bound articles require there to be a sufficient buildup in pressure for an adequately long time in order for the article walls to fully form and develop into an expanded cellular state.
  • Streaming is defined as the formation of flow fissures due to the turbulent expulsion of large amounts ofthe starch-bound composition in or around the area ofthe vent holes during the hardening of the article wall in the same area. Hardening of the molding composition near the vent holes together with continued flow or movement of the composition out the vent holes can cause significant weakening ofthe structural matrix.
  • any or all of the preceding problems associated with the molding of starch-based compositions can also occur as a result of maintaining the molding apparatus at the wrong temperature. It is known that increasing the mold temperature also has the effect of increasing the reactivity ofthe molding system. However, if the molding apparatus is too cool, the molding process can be prohibitively long and, hence, an expensive use of capital equipment. In addition, inadequately or nonuniformly heated molds can cause insufficient expansion of the starch-based composition and an insufficient buildup of pressure within the mold. This, in turn, can lead to an incompletely formed articles and/or collapse ofthe article wall, as discussed above.
  • the inventors have found that the molding process is much more forgiving and allows for far greater variations in the processing variables through the use of significant quantities of pregelatinized starch in the molding composition. This in turn makes it much easier to optimize the particular molding process being used to manufacture a desired starch-bound article.
  • significant increases in the window or range ofthe allowable processing variables such as water concentration, fill weight, and mold temperature have been observed for compositions which include significant quantities of pregelatinized starch.
  • pregelatinized starch within the molding composition in an amount in a range from about 12% to about 50% by weight ofthe overall starch content, more preferably in a range from about 15% to about 45% by weight, and most preferably in a range from about 20% to about 40% by weight.
  • pregelatinized starch will depend on the identity and concentration of the other components within the starch-based composition, such as fibers, inorganic fillers, and the like. It will also depend on the fill weight being employed, the temperature of the heated molding apparatus, and the shape or wall thickness ofthe article being manufactured. Finally, the optimal pregelatinized starch content will depend on the type of pregelatinized starch being used. Certain types of pregelatinized starch, such as corn starch, have much lower gelating power compared to pregelatinized potato starch, which is lower still compared to certain modified starches specifically designed to be powerful gelating agents.
  • the amount of pregelatinized starch should be great enough to cause the fluid fraction ofthe molding composition to have a viscosity of at least about 5000 cps, preferably greater than about 10,000 cps, and most preferably greater than about 25,000 cps, as measured on a Paar-Physica Oscillating Viscometer.
  • the compositions of the present invention allow for the manufacture of articles having wall thicknesses less than about 5 mm, typically less than about 2-3 mm, and even as low as 1 mm or less.
  • articles having thicknesses of about 2-3 mm or less have greater strength and durability and can be molded with even fewer defects compared to thicker articles using the compositions ofthe prior art.
  • the mechanism that is believed to be responsible for the ability of the pregelatinized starch to offset the usually deleterious effects of increasing system reactivity involves the partial occlusion of the vent holes during the molding process.
  • the inventors have found that optimal buildup of internal pressure within the molding apparatus occurs when the vent holes have become partially blocked or occluded as a result of the expulsion of a portion of the starch-bound composition during initial expansion. Hardening of the molding material around the interior surface of the vent holes results in the formation of a "donut-hole" or "straw" in the middle ofthe hardened material, which is sufficiently narrow to prevent further expulsion of appreciable amounts of the molding composition.
  • the partially occluded hole nevertheless allows for the escape of water vapor, particularly as the pressure increases within the mold due to the partial occlusion ofthe vent hole.
  • the narrow passage formed by the hardened molding material acts as a sort of filter that advantageously restricts the expulsion of molding material while providing a path for the escape of water vapor.
  • Evidence shows that there is a direct correlation between the amount of pregelatinized starch within the starch-based composition and the speed and reliability with which the partial occlusion ofthe hole occurs.
  • the partially occluded vent holes prevent, or at least greatly impede, the expulsion of excessive amounts of molding material, regardless ofthe rate and magnitude ofthe buildup of internal mold pressure.
  • the partially occluded vent holes still allow for the release of water vapor at about the same rate as through nonoccluded vent holes, and possibly at even higher rates if there is a substantial increase in internal mold pressure caused by increasing one or more ofthe system reactivity variables.
  • the formation of effectively smaller vent holes can result in the formation of hardened articles in an even shorter time period compared to articles using conventional compositions.
  • the tendency ofthe partially occluded vent holes to inhibit the expulsion ofthe molding composition also results in a significant reduction in the amount of flashing that forms on the outer edge ofthe molded article and which must be removed.
  • the heated molding apparatus causes the water within the composition to quickly heat up and vaporize, which causes the molding mixture to be expelled through the vent holes. While the heated water also causes the previously ungelatinized starch granules to gelate, the gelation reaction is dynamic and occurs over a period of time. Ungelatinized or only partially gelatinized starch is less sticky than fully gelatinized starch.
  • the starch-based composition that is expelled from the vent holes may not be sufficiently sticky to cause reliable adhesion ofthe starch-based composition to the inner walls ofthe vent holes.
  • the occlusion ofthe vent holes is thus much slower and more sporadic, which leads to the expulsion of far greater amounts ofthe starch-based composition. This, in turn can result in inadequate expansion of the composition and buildup of internal pressure within the molding apparatus, causing an inadequately formed part.
  • Figure 15 is a graph illustrating the operational windows of acceptable fill weights as a function of water content for a composition containing 75 g of pregel starch at 0.070" part thickness.
  • the present invention is directed to starch-based compositions used to mold starch-bound articles having a cellular structural matrix.
  • Such compositions include a significant quantity of pregelatinized starch, which significantly increases the operation windows for certain key variables known to affect system reactivity: water concentration, fill weight, mold temperature, and vent hole size. It has heretofore been necessary to maintain a careful balance in system reactivity in order to successfully mold articles of adequate mechanical strength and integrity.
  • articles made from such compositions have a foamed, inorganically filled starch-bound structural matrix, preferably reinforced with well-dispersed fibers and including an inorganic filler.
  • the pregelatinized starch also aids the ability to homogeneously disperse the fibers throughout the starch-based compositions to be molded (i.e., "molding compositions").
  • compositions and methods ofthe present invention yield a variety of articles, including containers, plates, cups, "clam shell” sandwich containers, platters, cartons, boxes and other types of containers and articles having mechanical properties substantially similar or even superior to articles manufactured using conventional materials, such as paper, polystyrene foam, plastic, metal and glass.
  • inventive articles can often be made at a fraction ofthe cost of their conventional counterparts due to their inclusion of the aforementioned components, which are generally very inexpensive, particularly the inorganic filler component, and also because of lower overall energy requirements.
  • the manufacturing processes and resulting articles are less harmful to the environment compared to conventional materials and processes.
  • Fourth, the inventive articles are of generally low mass.
  • the surface ofthe starch-bound articles can 18 be coated with appropriate coating materials in order to control their tendency to break down in the presence of moisture.
  • starch-based composition refers to starch-containing compositions of appropriate rheology that can be molded within heated molds to form articles having a starch-bound cellular matrix.
  • Such compositions typically include a gelatinized starch component that raises the viscosity to at least about 5,000 cps, an ungelatinized starch component that is gelatinized upon molding in heated molds, well-dispersed fibers, water, an inorganic filler, and, optionally, a mold-release agent, organic fillers, dispersants, cross-linkers, plasticizers, humectants, and integral coating materials.
  • pregel mixture refers to a mixture containing pregelatinized starch, water, and, optionally, solid components such as fibers.
  • the pregel mixture will typically be heated to gelatinize the starch and then cooled before adding the remaining ungelatinized starch and other components to form the molding mixture.
  • fluid fraction or liquid fraction
  • the fluid fraction shall refer to the fluid or liquid component within either the pregel mixture or starch-based composition, less the actual solids or solid components that are not dissolved within the fluid fraction.
  • the fluid fraction includes all components that are dissolved therein, even materials that were initially solid or which will return to a solid state later in the molding process.
  • the fluid fraction is characterized as having an approximate Binghamian flow characteristic due to the inclusion of pregelatinized starch and will have a viscosity of at least about 5000 cps. The increased viscosity and yield stress ofthe fluid fraction greatly aids in uniformly dispersing the fibers throughout the starch-based composition.
  • pregel refers to the gelatinized starch component or fraction within the molding composition that exists before the mixture is formed between heated molds.
  • the pregelatinized starch can be obtained by gelatinizing native, or unmodified, starch by heating the starch in water to above the gelation temperature ofthe starch.
  • pregel might comprise a modified starch that will gelate in "cold water", or water at room temperature. 15 holes is not so strong that it can totally withstand the gas-expelling forces within the mold; therefore, the smaller "donut hole” is maintained by the force of the water vapor that is continuously expelled through the vent holes.
  • vent hole size in the first instance will not have the same effect as the foregoing partial occlusion mechanism since sufficiently small vent holes can become completely blocked as a result ofthe hardening of the molding composition.
  • the hardened starch-based composition is able to form a durable skin having a thickness of 0.015
  • a vent hole having an initial width of 0.040" will have a resulting effective vent hole size of only 0.010" after partial occlusion (the 0.015" skin surrounding the effectively smaller vent hole effectively blocks 0.030" ofthe hole width).
  • decreasing the vent hole size substantially below 0.030" might and can result in complete blockage of the vent holes.
  • Figure 1 is a graph illustrating the operational windows of acceptable fill weights as a function of pregel starch content for a composition containing 1400 g of water at a
  • Figure 2 is a graph illustrating the operational windows of acceptable fill weights as a function of pregel starch content for a composition containing 1500 g of water at a 0.070" part thickness;
  • Figure 3 is a graph illustrating the operational windows of acceptable fill weights as a function of pregel starch content for a composition containing 1600 g of water at a 0.070" part thickness;
  • Figure 4 is a graph illustrating the operational windows of acceptable fill weights as a function of water content for a composition containing 100 g of pregel starch at a
  • Figure 5 is a graph illustrating the operational windows of acceptable fill weights as a function of water content for a composition containing 150 g of pregel starch at a 0.070" part thickness
  • Figure 6 is a graph illustrating the operational windows of acceptable fill weights as a function of water content for a composition containing 200 g of pregel starch at a 0.070" part thickness
  • Figure 7 is a graph illustrating the operational windows of acceptable fill weights as a function of temperature for a composition containing 1500 g of water at a 0.070" part thickness;
  • Figure 8 is a graph illustrating the operational windows of acceptable fill weights as a function of temperature for a composition containing 1400 g of water at a 0.070" part thickness;
  • Figure 9 is a graph illustrating the operational windows for acceptable lid fill weights as a function of pregel starch with and without 25% recycled material for a composition containing 1400 g of water at a 0.070" part thickness;
  • Figure 10 is a graph illustrating the operational windows of acceptable fill weights as a function of pregel starch for compositions containing 1400 g of water with and without 25% recycled parts at a 0.070" part thickness
  • Figure 11 is a graph illustrating the operational windows of acceptable fill weights as a function of temperature for compositions containing 1300 g of water and 0.25% guar gum at a 0.070" part thickness;
  • Figure 12 is a graph illustrating the operational windows of acceptable fill weights as a function of temperature for a composition containing 1500 g of water at a 0.070" part thickness;
  • Figure 13 is a graph illustrating the operational windows of acceptable fill weights as a function of water content for a composition containing 100 g of pregel starch at a 0.070" part thickness;
  • Figure 14 is a graph illustrating the operational windows of acceptable fill weights as a function of water content for a composition containing 100 g of pregel starch at
  • ungelatinized starch refers to native or otherwise ungelatinized starch or starch derivatives that can be added to the molding composition but which will not become gelatinized until the mixture has been heated to above the gelation temperature of the ungelatinized starch during the molding process.
  • the "total starch” in the starch-based composition comprises the combination of pregel starch and ungelatinized starch, which together constitute the "starch-based binder" upon the removal of part or substantially all ofthe free water (or unbound) from the molding composition.
  • starch-based gel shall refer to an aqueous gel formed by the gelation, or gelatinization, of any portion of the total starch. It does not refer to what has been referred to in the art as a "hot melt" or
  • destructurized starch which generally require the application of elevated temperatures and extremely high pressures (>600 Bars) for an extended period and with low water content in order for the starch to pass through a "glass transition phase” and thereby act as a thermoplastic.
  • a "hot melt” does not harden through the removal of water as does a starch-based gel but only upon cooling the melt to below the "glass transition temperature”.
  • total solids includes the actual solids together with any admixtures that may be added to the pregel mixture and or starch-based composition that are initially dissolved into the fluid fraction but which will form a solid upon the removal of water by evaporation during or after the molding process.
  • fiber-reinforced cellular matrix starch-bound cellular matrix or starch-bound matrix
  • starch-bound matrix shall refer to the substantially hardened structure ofthe articles manufactured herein.
  • hardening refers to the process of removing water from the molding mixture, particularly from the starch-based gel, to produce a form-stable article.
  • hardening is not limited by the extent of gelation ofthe ungelatinized starch component or the amount of water actually removed.
  • reactivity or "system reactivity”, as used in the specification in the appended claims, refer to both the rate and magnitude of pressure build-up within the heated molding apparatus due to the vaporization of water. Hence, system reactivity increases as either the rate or magnitude of pressure increases.
  • the factors which tend to increase the rate and or the magnitude of water vapor pressure include increasing the water concentration, fill weight, mold temperature, and vent hole size.
  • form-stable as used in the specification and the appended claims, refers to the state in which the starch-bound matrix of the newly demolded article has sufficient strength and structural integrity that it can be removed from the mold, support its own weight against the force of gravity, resist destructive water vapor expansion, and resist significant deformation when exposed to subsequent processing and handling.
  • Containers and other articles that can be formed using the compositions and processes ofthe invention include, but are not limited to, the following: cartons, boxes, sandwich containers, hinged or two- part "clam shell” containers, dry cereal boxes, frozen food boxes, milk cartons, fruit juice containers, carriers for beverage containers, ice cream cartons, cups (including, but not limited to, disposable drinking cups and cone cups), french fry scoops, fast-food carry out boxes, packaging, support trays (for supporting products such as cookies and candy bars), cans, yoghurt containers, sleeves, cigar boxes, confectionery boxes, boxes for cosmetics, plates, vending plates, pie plates, trays, baking trays, bowls, breakfast plates, microwaveable dinner trays, "TV” dinner trays, egg cartons, meat packaging platters, disposable single use liners which can be utilized with containers such as cups or food containers, cushioning
  • the molding compositions used to manufacture the starch-bound articles ofthe present invention include starch as the primary binder, which acts as a binder through the formation of a starch gel and subsequent removal of water by evaporation from the starch gel.
  • Starch is a natural carbohydrate chain comprising primarily condensed glucose molecules. Plants manufacture and store starch in granular form.
  • Starch granules comprise two types of glucose polymers: the single-chain amylose that is generally soluble in water and other solvents and the branched amylopectin that is less soluble in water.
  • Amylose molecules have a molecular weight in a range from about 40,000 to about 650,000 while amylopectin molecules have a molecular weight of about 10,000,000 to about 100,000,000.
  • starch granules are insoluble in cold water and are gelatinized by raising the water temperature to above the gelatin temperature of the starch granules. When the starch granules are exposed to hot water, the granule walls soften, swell, and then burst to release the starch chains, which result in the gelation ofthe liquid fraction of the mixture.
  • the exact temperature at which a particular starch granule swells and gelates depends on the type of starch it is. Cornstarch, for example, gelates at a higher temperature than potato starch. Unmodified starch granules can be gelated in cold water if the outer membrane has been broken by, e.g., grinding the starch granules.
  • starch can be chemically modified so that it will gelate in cold water. Gelation is a result of the amylose and amylopectin chains, which are initially compressed within the granules, stretching out and intertwining with each other. After the water has been removed, the resulting mesh of inter-connected polymer chains forms a solid material that can have a tensile strength up to about 40-50 MPa.
  • the hardened amylose and amylopectin polymers are used in the present invention to bind individual filler particles and fibers within the molding composition.
  • starch is produced in many plants, an important source are seeds of cereal grains (e.g., corn, waxy corn, wheat, sorghum, rice, and waxy rice). Another important source includes tubers such as potatoes, roots such as tapioca (i.e., cassava and manioc), sweet potato, and arrowroot, and the pith ofthe sago palm.
  • tubers such as potatoes, roots such as tapioca (i.e., cassava and manioc), sweet potato, and arrowroot, and the pith ofthe sago palm.
  • starch includes both unmodified and modified starches.
  • modified it is meant that the starch can be derivatized or modified by typical processes known in the art such as, e.g., substitution, esterification, etherification, oxidation, acid hydrolysis, cross-linking, and enzyme conversion.
  • Typical modified starches include esters, such as the acetate and the half-esters of dicarboxylic acids/anhydrides, particularly the alkenylsuccinic acids/anhydrides; ethers, such as the hydroxyethyl and hydroxypropyl starches; oxidized starches, such as those oxidized with hypochlorite; starches reacted with cross-linking agents, such as phosphorus oxychloride, epichlorohydrin, hydrophobic cationic epoxides, and phosphate derivatives prepared by reaction with sodium or potassium orthophosphate or tripolyphosphate, and combinations thereof.
  • esters such as the acetate and the half-esters of dicarboxylic acids/anhydrides, particularly the alkenylsuccinic acids/anhydrides
  • ethers such as the hydroxyethyl and hydroxypropyl starches
  • oxidized starches such as those oxidized with hypochlorite
  • Modified starches also include seagel, long-chain alkylstarches, dextrins, amine starches, and dialdehyde starches. Although all starches used in the present invention are originally ungelatinized but then become gelatinized at some point in the manufacturing process, the molding composition will include both a pregelatinized and ungelatinized starch component. Pregelatinized starches include starches that have previously been gelatinized before formation ofthe final molding composition. The pregelatinized starch component within the molding composition can either consist of modified starches that are gelated in cold water, unmodified starches that are gelated and then cooled prior to forming final molding composition, or both. In addition, unmodified starches can be gelatinized, cooled, dried, and then supplied in powder form that is capable of gelating again in cold water.
  • the increased viscosity and yield stress ofthe mixture resulting from the pregel starch component are necessary in order to (1) control, moderate, and offset fluctuations in system reactivity, and (2) to aid in the dispersion of the fibrous component.
  • the pregelatinized starch component will be included in an amount in a range from about 12% to about 50% by weight of the total starch within the starch-based composition, preferably in a range from about 15% to about 45% by weight, and most preferably in a range from about 20% to about 40% by weight.
  • the unmodified starch component will generally comprise the majority of total starch within the molding composition. In its unmodified, granular state, unmodified starches will not gelate in cold water and do not appreciably affect the rheology of the liquid fraction of the molding composition. Hence, unmodified starch can be included in significantly large amounts without greatly affecting the rheology of the molding composition since their primary effect on system rheology is negligible until the composition is heated during the molding process. Once the starch-based composition has been properly positioned within the heated molds, the increased viscosity and green strength imparted by the newly gelated unmodified starch component is advantageous.
  • the unmodified starch component within the starch-based composition of the present invention will be included in an amount in a range from about 50% to about 88% by weight of total starch within the molding composition, preferably in a range from about 55% to about 85% by weight, and most preferably in a range from about 60% to about 80% by weight.
  • the balance between the pregelatinized starch and unmodified starch component should be adjusted in order to yield a fluid fraction having the proper rheology.
  • the fluid fraction will have the viscosity of at least about 5,000 cps, as measured on a Paar-Physica Viscometer, more preferably greater than 10,000 about cps. and most preferably greater than about 25,000 cps.
  • different types of pregelatinized starch have varying gelating powers. The greater the gelating power, the greater the viscosity-increasing effect of the pregelatinized starch within the fluid fraction.
  • the magnitude of gelating power can be determined for any pregelatimzed starch by means of a Brabender Viscometer.
  • the Brabender Viscometer measures the gelating power of the pregelatinized starch in terms of the torque exerted by the viscometer and expressed in Brabender Units (BU).
  • BU Brabender Units
  • one type of modified starch known as Paselli PGF has a gelating power of 2000 BU, while Paselli P has a gelating power of 1800 BU.
  • the greater the gelating power the less pregelatinized starch will be necessary to increase the viscosity of the fluid fraction to a desired level.
  • 12% by weight of total starch of a pregelatinized starch having a very high gelating power might be sufficient, it may be necessary to use greater amounts of pregelatinized starch having significantly lower gelating power.
  • unmodified starch granules which are typically far less expensive compared to modified starches.
  • unmodified starch granules derived from potato starch are very inexpensive and are often treated as useless waste products. In some countries it is discarded or fed to cattle as a cheap feed material.
  • the use of unmodified starches in the present invention provides a tremendous economic advantage over other materials and also provides a useful outlet for such previously discarded materials.
  • Preferred modified starches include those that gelate and produce a high viscosity, high yield stress composition at a relatively low temperature.
  • a preferred starch is potato starch, which quickly gelates and reaches a maximum viscosity and yield stress at about 65 °C. The viscosity and yield stress of a mixture containing gelatinized potato starch and water then decreases as the temperature is raised further.
  • Waxy corn starch acts in a similar fashion and is also preferred. Potato and waxy corn starch are also preferred because they swell and gelate easily in a single step; however, any starch that has similar swelling characteristics will be preferred to those that swell in two or more stages.
  • ungelatinized starches within the molding compositions to regulate the foamed structural matrix.
  • the viscosity and yield stress of a mixture containing corn starch gradually increases as the temperature increases.
  • corn starch produces a relatively low viscosity, low yield stress composition compared to potato starch at 65 °C, but produces a relatively high viscosity, high yield stress composition, compared to potato starch at 95 °C.
  • greatly elevated viscosity and yield stress ofthe mixture at the interior section ofthe article can be quickly reached and then maintained as the starch-based composition is heated to form the cellular matrix ofthe article.
  • the increased viscosity decreases the cell size and increases the cell wall thickness, thereby increasing the fracture toughness ofthe article as it is being molded.
  • Water is a key ingredient within the compositions of the present invention because it affects so many variables.
  • water aids in the dispersion of the fibrous component throughout the starch-based composition by forming a high yield stress, high viscosity fluid fraction with the pregelatinized starch component.
  • the starch gel containing fluid fraction aids in the partial occlusion or blockage ofthe vent holes during the molding process, which is a critical step or factor in controlling system reactivity.
  • the partial occlusion of the vent holes occurs as the starch gel of the fluid fraction releases the water by evaporation as a result ofthe heated molds.
  • water is important for overall molding composition rheology in order to obtain a molding composition that can be readily mixed, transported, and injected into the molding apparatus.
  • the water is important in lubricating the solid particles, solvating the dissolvable or gelatable components and in achieving the proper viscosity of the composition.
  • the water is an important component within the fluid fraction that aids in the homogenous dispersion of the fibers component. Nevertheless, in combination with the pregel starch, far less water is required to disperse the fibers compared to, e.g., highly aqueous slurries used in the paper industry.
  • the water acts as a gelating agent that gelates the ungelatinized starch granules during the heated molding process, wherein the molding compositions are placed between heated molds.
  • the subsequent removal of water by evaporation from the total starch gel formed by the pregelatinized and the newly gelatinized starch granules causes the starch component to solidify and act to bind the solid components together within the molded article.
  • the water greatly affects the system reactivity, which is directly related to the rate and magnitude ofthe formation of pressure within the heated molds as the water changes from a liquid to a gaseous state upon heating.
  • the greater the rate or formation and magnitude of internal pressure the greater the force with which the starch- based composition expands and is expelled from the vent holes.
  • Prior art compositions included little or no pregelatinized starch. Hence, only that starch that had attained a gelatinized state before the composition was expelled through the vent holes could form the skin on the vent hole wall. The result was the undesired expulsion of excessive amounts ofthe starch compositions.
  • pregelatinized starch in significant amounts within the compositions of the present invention aids in the quick formation of a skin within the interior of the vent holes, which causes the desired partial occlusion and, hence, a moderation of system reactivity. Partial occlusion ofthe vent holes prevents, or least greatly inhibits, the further expulsion of substantial amounts ofthe molding composition while allowing for the free escape of the water vapor being driven off from the composition by the heated molds.
  • the water also serves the function of creating a fluid fraction having the desired rheological properties, including yield stress, viscosity, and flowability. These properties are general ways of approximating the "workability" or flow properties of a mixture.
  • the yield stress and viscosity ofthe mixtures ofthe present invention may range from being relatively low (similar to that of a thin batter) up to being very high (similar to paste or clay). Preferably, the viscosity will be above about 5,000 cps, more preferably greater than about 10,000 cps. Where the viscosity is so high that the material is initially dough ⁇ like in the green state, it is generally better to refer to the yield stress, rather than the viscosity, ofthe mixture.
  • the yield stress is the amount of force necessary to deform the mixture.
  • a sufficient amount of water should be added to disperse and uniformly gelate the starch within the molded starch-based composition.
  • the water content should also be sufficient to function with the particular processing equipment being employed.
  • Compositions with high viscosity and yield stress may require an auger apparatus to mix and convey the composition to the molding apparatus.
  • lower viscosity compositions can be prepared using conventional mixers and then transferred to the molds using conventional pumps.
  • High yield stress compositions having a consistency similar to that of clay or dough can be cut into small portions, which can then be mechanically placed between the molds.
  • Increasing the water content also increases the number and size of the cells or voids in the structural matrix and lowers the density of the resulting article.
  • the more water in a mixture the more vapor that is produced, and thus, the more cells in the interior and the more pinholes in the surface that are formed. If the water content is too high, the composition may be unable to produce form-stable, crack free articles. In contrast, using less water yields a more dense product having smaller cells. Based on the above discussion, the percentage of water within the starch-based composition depends in part on the processing equipment, the desired viscosity, the pregelatinized starch content, and the desired mechanical properties ofthe final molded article.
  • the amount of water that is added to the mixtures ofthe present invention will preferably be in a range from about 15% to about 80% by total weight ofthe mixture, the exact amount depending on the desired viscosity ofthe moldable composition, and more preferably from about 30% to about 70% by weight.
  • Fibers and “fibrous materials” include both inorganic fibers and organic fibers.
  • the use of fibers has been found to provide a number of useful benefits. Fibers serve to reinforce the structural matrix ofthe molded articles. More specifically, they serve to increase the cohesion of the partially hardened articles, giving them increased form stability; they also increase the elongation, deflection, toughness, fracture energy, flexural strength, and tensile strength ofthe articles. Fibers also aid retaining small amounts of residual water within the newly molded articles by preventing collapse or over expansion of the cellular structural matrix due to the softening effect ofthe water. In the prior art, articles had to be over dried in order to be successfully demolded, then conditioned to reimpart moisture and reduce brittleness.
  • the fibers will have a length greater than about 3.5 mm and an aspect ratio of at least about 100:1. Of equal or greater importance is the level of dispersion of the fibers. More homogenous dispersion ofthe fibers results in far greater strength and toughness of the final product. On the other hand, poorly dispersed or clumped fibers often result in a decrease in strength compared to compositions in which no fibers are used. In accordance with the present invention, the use of significant quantities of pregelatinized starch results in substantially homogenous dispersion of fibers throughout the starch-based composition.
  • Fibers that may be used preferably include naturally occurring organic fibers, such as cellulosic fibers extracted from hemp, cotton, plant leaves, sisal, abaca, bagasse, wood (both hardwood or softwood, examples of which include southern hardwood and southern pine, respectively), or stems, husks, shells, and fruits, or inorganic fibers made from glass, graphite, silica, ceramic, or metal materials. Any equivalent fiber which imparts strength and flexibility is also within the scope of the present invention. The only limiting criteria is that the fibers impart the desired properties without adversely reacting with the other constituents ofthe inorganically filled material and without con ⁇ taminating the materials (such as food) stored or dispensed in articles made from the material containing such fibers.
  • naturally occurring organic fibers such as cellulosic fibers extracted from hemp, cotton, plant leaves, sisal, abaca, bagasse, wood (both hardwood or softwood, examples of which include southern hardwood and southern pine, respectively), or stems, husks,
  • Recycled paper fibers can be used, but they are somewhat less desirable because ofthe fiber disruption that occurs during the original paper manufacturing process.
  • sisal fibers are available from International Filler
  • abaca fibers are available from Isarog Inc. in the Philippines
  • glass fibers such as Cemfill®, are available from Pilkington Co ⁇ oration in England.
  • fibers allow for much greater variability in the final water content of demoldable articles. For example, in the case where all of the water is removed from the mixture by evaporation, the fibers will prevent cracking of the structural matrix because they reinforce the entire matrix and prevent the article from shrinking. On the other hand, where the article is removed while still having substantial amounts of free water within the structural matrix, which would normally lead to expansion and rupture ofthe structural matrix due to internal water vapor pressure within the hot demolded articles, the fibers provide an internal strengthening effect. In addition, fibers are able to hold and then release water into the structural matrix, which increases the toughness and flexibility of this article.
  • the amount of fibers added to the molding composition will vary depending upon the desired properties of the final molded article.
  • the flexural strength, toughness, flexibility, and cost are principle criteria for determining the amount of fiber to be added to the composition.
  • the concentration of fibers will preferably be in a range from about
  • the molding composition 1% to about 40% by weight ofthe molding composition, more preferably from about 2% to about 20% by weight, and most preferably from about 3% to about 10% by weight.
  • fillers includes both inorganic and inert organic filler particles but do not typically include fibers, except fibrous materials having very low aspect ratio and which impart little or no strengthening effect. In general, fillers do not strengthen the structural matrix, but merely add mass and reduce the starch requirements. There are a variety of types of fillers that can be used in the present invention.
  • the size ofthe inorganic filler particles will generally be many times greater than the particles ofthe inorganic filler materials typically used in the paper industry, which greatly reduces their cost.
  • useful inorganic fillers include perlite, vermiculite, sand, gravel, rock, limestone, sandstone, glass beads, aerogel, xerogels, seagel, mica, clay, synthetic clay, alumina, silica, fly ash, fused silica, zeolites, tabular alumina, kaolin, microspheres, hollow glass spheres, porous ceramic spheres, gypsum (calcium sulfate dihydrate), calcium carbonate, calcium aluminate, lightweight polymers, xonotlite (a crystalline calcium silicate gel), lightweight expanded clays, hydrated or unhydrated hydraulic cement particles, pumice, exfoliated rock, and other geologic materials.
  • inorganic fillers include perlite, vermiculite, sand, gravel, rock, limestone, sandstone, glass beads, aerogel, xerogels, seagel, mica, clay, synthetic clay, alumina, silica, fly ash, fused silica, zeolites, tabular
  • a dry-milled calcium carbonate is a preferred inorganic aggregate, since it can be obtained at one-third the cost of calcium carbonate obtained through wet-milling.
  • a preferred calcium carbonate is R040, which has a particle size range from about 10 to 150 microns, with an average particle size of about 42 microns, and a low specific surface area.
  • Both clay and gypsum are particularly important aggregate materials because of their ready availability, extreme low cost, workability, ease of formation, and because they can also provide a degree of binding and strength if added in high enough amounts (in the case of gypsum hemihydrate). Because gypsum hemihydrate can react with the water within the molding composition, it can be employed as a means for hardening, or at least increasing the form stability of, the molding composition.
  • fillers having a high amount of interstitial space in order to impart an insulation effect within the molded articles.
  • fillers which can add a lightweight characteristic and higher insulation to the molded articles include perlite, vermiculite, glass beads, hollow glass spheres, synthetic materials
  • porous ceramic spheres e.g., porous ceramic spheres, tabular alumina, etc.
  • cork e.g., cork, pumice, and lightweight expanded clays, sand, gravel, rock, limestone, sandstone, and other geological materials.
  • the inorganic filler is included in an amount in a range from about 20% to about
  • inert organic fillers will preferably be included in an amount in a range from about 5% to about 60% by weight of the total solids.
  • lightweight fillers defined as those having a density lower than about 1 g/cm 3 , are preferably included in an amount in a range from about 5% to about 85% by volume of the inorganically filled molding composition, more preferably from about 15% to about 65%, and most preferably from about 25% to about 55% by volume.
  • a mold-releasing agent can be added to the moldable composition.
  • Medium- and long-chain fatty acids, their salts, and their acid derivatives can be used as mold-releasing agents.
  • Preferred mold-releasing agents for use in the present invention include stearates, which have hydrophobic properties and are not soluble in water.
  • Stearate are salts of stearic acid and have the general formula of CH 3 (CH 2 ) 16 COO ' X + , where X + can be an ion of Al, Mg, Na, K, or Ca.
  • Aluminum stearate is one preferred mold release agent that has been approved by the FDA. Generally, a lower melting point or increased amount of stearate will give a smoother surface to a formed article. Stearates are grease repellant or resistant, allow the molding time of a product to be reduced, give a better surface content, provide heat transfer, and produce a continuous phase. When a clean mold is used to form products, a seasoning process takes place by using the stearates in the composition to be formed.
  • Silicones can also be used as mold releasing agents.
  • Lecithin which is a mixture of phosphatides and glycerides, can contribute to lessening of the stickiness of the molding composition, providing mold releasing properties, and can improve the flexibility of the formed articles.
  • Various waxes such as paraffin and bees wax, and
  • Teflon-based materials can also be used as mold-releasing agents.
  • One of the added benefits of using wax is that it can also act as an integral coating material, as discussed later.
  • Other materials, such as CaS and calcium silicate have also been found to work as mold-releasing agents.
  • the molds can be polished, chrome plated, or coated with, e.g. , nickel, Teflon, or any other material that limits the tendency ofthe articles to stick to the molds.
  • the above mold-releasing agents are preferably added to the starch-based compositions in a range from about 0.05% to about 15% by weight ofthe total solids, more preferably in a range from about 0.1 % to about 10% by weight, and most preferably in a range from about 0.5% to about 1% by weight. It is preferred to use a smaller amount of mold-releasing agents since agents such as stearates are relatively expensive.
  • the articles of manufacture ofthe present invention are produced through a multi- step process, which includes preparing the mixture and then molding the composition at an elevated temperature into the desired articles. Additional optional processing steps may include, for example, printing, coating, conditioning, and packaging of the final articles.
  • mixing means be able to yield a starch-based composition in which all of the components, particularly the fibrous material, are substantially homogeneously mixed throughout the composition.
  • high shear and low shear mixing apparatus are preferred depending on the stage ofthe mixing process.
  • the formation ofthe pregel mix and also the dispersion of fibers is carried out using a high shear mixing apparatus.
  • variable speed mixer can be used to provide both high and low shear mixing.
  • Variable speed mixers include the Eirich Rv-11.
  • An example of a low shear mixer is a Hobart Mixer.
  • the entire mixing process used to manufacture the starch-based molding composition can be carried out at room temperature.
  • unmodified starch granules such as potato starch or corn starch
  • the starch-based composition is ready for molding. It may be desirable at this stage to increase the water content in order to adjust the viscosity of the molding composition to a desired level.
  • a more detailed description of mixing processes that may be used to form starch-based compositions in general is set forth in the '783 Application, refereed to above and inco ⁇ orated by reference.
  • vent holes having a width in a range from about 0.030 close to about 0.060", more preferably in a range from 0.035" to about 0.050", and most preferably in a range from about 0.040" to about 0.045".
  • the molding apparatus should be heated to a temperature that is sufficiently high to cause the rapid expansion of a starch-based composition within the molding apparatus and also in order to drive off a substantial portion of the water by evaporation.
  • the molding apparatus should be heated to a temperature greater than about 145°C, more preferably greater than about 175°C, and most preferably greater than about 195°C.
  • the temperature should not be so great, however, so as to cause burning, scorching or carmelization of the starch binder. This generally occurs at temperatures greater than about 250°C.
  • compositions and methods disclosed herein By using the compositions and methods disclosed herein, a wide variety of different articles can be molded that will have adequate strength and structural integrity to be demolded and then shipped to the desired destination without the need for a subsequent lengthy conditioning step.
  • the ability to manufacture articles without a conditioning step, or simply a very short conditioning step, is a significant improvement over the prior art.
  • Coatings can be used to alter the surface characteristics ofthe articles in a number of ways, including sealing and protecting the articles, providing a more finished surface to the articles, and providing additional strength.
  • the use of coatings can provide protection against moisture, base, acid, grease, and organic solvents. Coatings provide a smoother, glossier, or scuff-resistant surface, and may even reinforce the article, particularly at a bend, fold, edge or corner. Some ofthe coatings can also be utilized as laminating materials or as adhesives.
  • D. Erjniing It may be desirable to apply print or other indicia, such as trademarks, product information, container specifications, or logos, on the surface ofthe article.
  • print or other indicia such as trademarks, product information, container specifications, or logos
  • This can be accomplished using any conventional printing means or processes known in the art of printing paper or cardboard products, including planographic, relief, intaglio, porous, and impactless printing.
  • Conventional printers include offset, Van Dam, laser, direct transfer contact, and thermographic printers. However, essentially any manual or mechanical means can be used.
  • the flexural strength ofthe final molded articles will generally be in a range from about 0.5 MPa to about 30 MPa, preferably from about 1 MPa to about 15 MPa, and more preferably from about 2 MPa to about 10 MPa.
  • the tensile strength ofthe final molded articles will generally be in a range from about 0.5 MPa to about 20 MPa, preferably from about 0.75 MPa to about 10 MPa, and more preferably from about 1 MPa to about 5 MPa.
  • the tensile and flexural fracture energy, defined as the area under a stress/strain curve, of the final molded articles will generally be in a range from about 100 J/m 2 to about 10,000 J/m 2 , preferably from about 300 J/m 2 to about 5000 J/m 2 , and more preferably from about 600 J/m 2 to about 1000 J/m 2 Because ofthe combination of high strength and low density made possible by the compositions and methods ofthe present invention, the specific strength or fracture energy of the articles, or strength or fracture energy values that have been normalized with respect to the density of the articles, will be significantly higher than what was possible according to the prior art.
  • the specific flexural strength of the articles will generally be in a range from about 0.5 MPa (g/cm 3 ) to about 60 MPa (g/cm 3 ), preferably from about 1 MPa/(g/cm 3 ) to about 40 MPa/(g/cm 3 ), and more preferably from about 2 MPa/(g/cm 3 ) to about 20 MPa/(g/cm 3 ).
  • the specific tensile strength ofthe articles will generally be in a range from about 0.5 MPa/(g/cm 3 ) to about 30 MPa (g/cm 3 ), preferably from about 0.75 MPa/(g/cm 3 ) to about 20 MPa/(g/cm 3 ), and more preferably from about 1 MPa/(g/cm 3 ) to about
  • the specific fracture energy ofthe articles will generally be in a range from about 1000 (J/m 2 )/(g/cm 3 ) to about 10,000 (J/m 2 )/(g/cm 3 ), preferably from about 2000 (J/m 2 )/(g/cm 3 ) to about 7500 (J/m 2 )/(g/cm 3 ), and more preferably from about 3000 (J/m 2 )/(g/cm 3 ) to about 5000 (J/m 2 )/(g/cm 3 ).
  • the articles ofthe present invention will generally have a normalized flexural strength with respect to the weight fraction of starch-based binder of about 5 MPa/(wt. fraction of starch-based binder) to about 100 MPa/(wt. fraction of starch-based binder), preferably from about 10 MPa (wt. fraction of starch-based binder) to about 75 MPa (wt.
  • the articles will generally have a normalized tensile strength with respect to the weight fraction of starch-based binder of about 3 MPa/(wt. fraction of starch-based binder) to about 50 MPa/(wt. fraction of starch-based binder), preferably from about 4 MPa/(wt. fraction of starch-based binder) to about 30 MPa/(wt. fraction of starch-based binder), and more preferably from about 5 MPa/(wt. fraction of starch-based binder) to about 20 MPa/(wt. fraction of starch-based binder).
  • the articles will generally have a normalized fracture energy with respect to weight fraction of starch-based binder of about 2000 (J/m 2 )/(wt. fraction of starch-based binder) to about 30,000 (J/m 2 )/(wt. fraction of starch-based binder), preferably from about 3000 (J/m 2 )/(wt. fraction of starch-based binder) to about 15,000 (J/m 2 )/(wt. fraction of starch-based binder), and more preferably from about 5000 (J/m 2 )/(wt. fraction of starch- based binder) to about 10,000 (J/m )/(wt. fraction of starch-based binder).
  • the range of strain ofthe articles (i.e., the amount of strain before rupture) will generally be in a range from about 1% to about 15%, preferably from about 1% to about 10%, and more preferably from about 1 % to about 5%.
  • the articles of the present invention will generally have low density, which reduces the overall weight per article as well as the mass of material that must be used initially to produce the articles and then be discarded or recycled when the article has completed the duration of its intended use.
  • the articles of the present invention will generally have a density in a range from about 0.05 g/cm 3 to about 1 g/cm 3 , preferably from about 0.1 g/cm 3 to about 0.5 g/cm 3 , and more preferably from about 0.15 g/cm 3 to about 0.3 g/cm 3 .
  • the articles can be characterized as having a laminate-type structure; there is an outer skin layer having a relatively high density and an interior foam portion having a lower density.
  • the outer skin layer is created instantaneously when the molding composition is contacted with the mold.
  • the pores formed in the interior foam portion can have a diameter of about 0.25 mm or greater.
  • the interior foam portion hardens when the moisture is removed during the molding process. By increasing the water content, the density of the final product will be lowered. Due to the ability of the compositions ofthe present invention to control or offset increases in system reactivity, the rate at which the moisture is driven off can be increased by, e.g., increasing the mold temperature without negatively altering the quality of the molded article. This is in contrast to the prior art, wherein increased water usually required for longer molding times. 35
  • Example Group 1 Various starch-based compositions were tested to determine the effect of varying amounts of pregelatinized starch on the ability to mold articles of acceptably high quality as the water concentration and fill weight were systematically varied. Each ofthe starch- based compositions included the following components:
  • the unmodified starch comprised
  • Avebe potato starch granules The fibers comprises natural, unbleached Arauco Celso softwood fibers.
  • the pregelatinized starch comprised Paselli PGF, a modified potato starch including phosphate functional groups and having a gelating power of 2000 Brabender Units (4% solution in water at 20° C) as measured on a Brabender Viscometer.
  • Starch-based compositions having varying amounts of unmodified starch, pregelatinized starch, and water were tested. Varying amounts of each of the compositions were placed in the molds. Every variation of the components and fill weight constituted a separate test run. Each test run was molded into 4 separate lids used in a two-part clam shell sandwich container having a fully detachable lid and base.
  • the molding apparatus used in each case comprised a four-cavity machined aluminum mold, including four matching male and female counte ⁇ arts, all maintained at a temperature of approximately 195° C.
  • Each of the individual male and female mold counte ⁇ arts included 4 vents, each vent having a width of 0.045" and a depth of 0.105".
  • Example Group 1 The stop height ofthe molds as they were brought together was 0.129" in each case.
  • Each ofthe molded lids had a wall thickness of approximately 0.070".
  • the average part weight for each test run was determined by averaging the part weights determined for each ofthe 4 separately molded lids. Table 1 shows the results ofthe tests conducted in Example Group 1.
  • min refers to the minimum fill weight required to form a complete part.
  • max refers to the maximum fill weight that resulted in a high quality part.
  • Figure 1 shows the operational window for fill weight (the ability to vary the fill weight while still molding high quality lids) as a function of pregel content for a mix design containing 1400 g water.
  • the largest operational window, or ability to vary the fill weight while still molding high quality lids, occurs at a pregel starch concentration of 150 g (30%), although the fill weight operational windows for compositions containing 20% (100 g) and 40% (200 g) pregel starch, respectively, are larger than for compositions using either more or less pregelatinized starch.
  • Figure 2 is similar to Figure 1 , except that it shows the operational windows for a starch-based composition having 1500 g water. Note that all three operational windows for the various pregel concentrations are quite large.
  • Figure 3 is also similar to Figure 1 , except that it shows the operational windows for a starch-based composition having 1600 g water. Note that acceptable operational windows occur only at pregel starch concentrations of 20% (100 g) and 30% (150 g), but not for 40% (200 g). In addition, the operational windows are much larger when 1400 g or 1500 g of water is employed rather than 1600 g water.
  • Figure 4 shows the operational window for fill weight as a function of water content for a mix design containing 100 g (20%) pregelatinized starch.
  • the fill weight operational windows for compositions containing 1400 g and 1600 g water, respectively are larger than for compositions in which the water content is outside this range, the largest operational window occurs at a water content of 1500 g.
  • Figure 5 is similar to Figure 4, except that it shows the operational windows for a starch-based composition having 150 g (30%) pregelatinized starch. Note that the two operational windows for water contents of 1400 g and 1500 g, respectively, are considerable, although the size ofthe operational window drops off sha ⁇ ly for 1600 g water.
  • Figure 6 is also similar to Figure 4, except that it shows the operational windows for a starch- based composition having 200 g (40%) pregelatinized starch. Note that the two operational windows for water contents of 1400 g and 1500 g, respectively, are large, whereas the operational window for compositions containing 1600 g water is nonexistant.
  • Ultra Crisp is a modified corn starch available from National Starch.
  • the pregel mix was cooled to below the gelatin temperature before adding the remaining ungelatinized starch.
  • the starch-based composition was molded into sets of 4 clam shell lids using the methods and molding apparatus of Example Group 1 , except that the temperatures ofthe top (male) and bottom (female) molds were varied.
  • the width of the vent holes was reduced to 0.040" from 0.045" while the number of vent holes per mold pair was increased from up to 8.
  • the temperature ofthe 4 bottom molds was varied from approximately 160° C to about 210° C in 10° intervals, while the temperature ofthe top mold was kept approximately 5° higher than the bottom mold.
  • Example Group 3 A study similar to the one set forth in Example Group 2 was conducted using the following starch-based composition:
  • the starch-based composition was molded into sets of 4 clam shell lids using the methods and molding apparatus of Example Group 2.
  • the bottom mold was varied between approximately 160° C and about 210° C and the top mold was varied between approximately 165° C and about 215° C in 10° intervals.
  • the examples illustrate the difficulty in maintaining the exact same mold temperature during each interval.
  • the fill weight, or amount ofthe starch-based composition placed between the molds was varied for different mold temperatures in order to demonstrate the operational windows for both fill weight and mold temperature for the above starch-based composition, which included 20 % by weight pregelatinized starch.
  • Table 3 shows the results ofthe tests conducted in Example Group 3. Table 3
  • Figure 8 shows the operational window (min. and max.) for fill weight as a function of average mold temperature for the mix design used in each ofthe test runs of Example Group 3.
  • Figure 8 shows that the operational window of acceptable fill weights increases as the temperature is increased, particularly as the average mold temperature is increased above about 195° C.
  • Figure 8 clearly illustrates the advantage of using significant quantities of pregelatinized starch as a means for increasing the operational windows for both fill weight and mold temperature.
  • Example Group 4 Two different starch-based compositions were provided and then tested using the molding apparatus and methods set forth in Example Group 2.
  • One ofthe compositions included a significant amount of recycled material, i.e., from previously manufactured containers. This was done to determine if gelatinized starch from the molded composition could be substituted for some of the pregelatinized starch added to the starch-based composition while still obtaining the beneficial effects ofthe pregelatinized starch.
  • Recycled articles would provide a very inexpensive source of gelatinized starch.
  • Sources of recycled material include not only post-consumer container products but also molded compositional material that is accumulated at the manufacturing site as a result of, e.g., defective articles and flashing material.
  • the first composition designated as Composition 1, included the following components:
  • Ungelatinized Starch 400 g Paselli PGF (pregel) 100 g Composition 2 was derived from Composition 1 by reducing the amount of Paselli PGF from 100 g to 50 g, while including 25% recycled material by weight of total solids in Composition 2.
  • the recycled material was derived from a basic starch-based composition similar to either Composition 1 or 2.
  • the starch component within recycled articles is substantially gelatinized; hence, the recycled component of Composition 2 provides a source of pregelatinized starch that would be expected to increase the operational windows as other forms of pregelatinized starch have done.
  • gelatinized starch derived from recycled material would be expected to have significantly lower gelating power compared to newly gelatinized starch granules and, particularly, specially modified starches such as Paselli PGF.
  • the recycled material undoubtedly contained far greater than 50 g gelatinized starch, which was the amount ofthe reduction in weight ofthe Paselli PGF.
  • Figure 9 shows the operational window of allowable fill weights that will yield articles of superior quality for both Composition 1 and Composition 2, which are identified by the amount of Paselli PGF and recycled material: PGF 100 is Composition 1 and PGF 50 + 25% recycle is Composition 2. Note that the fill weight operational window is slightly larger for Composition 1 , while the average fill weight within the operational window for Composition 2 is slightly larger. Hence, Figure 9 illustrates that enlarged operational windows may be obtained where pregelatinized starch is used in increased quantities, regardless ofthe form or source ofthe pregelatinized starch.
  • Example Group 5 Five different compositions were tested in similar fashion as in Example Group 4 in order to determine the effect of adding recycled material as a source of pregelatinized starch, along with varying amounts of Paselli PGF modified starch.
  • the first composition designated as Composition 1, included the following components:
  • Compositions 2-5 were formed by adding recycled material to Composition 1 in an amount of 25 % by weight of total solids and also reducing the concentration of Paselli PGF pregel in 25 g increments as follows:
  • Figure 10 shows the operational window of allowable fill weights that will yield articles of superior quality for Compositions 2-5, which are identified by the concentration of PGF pregel starch (e.g., Composition 5: 0 g; Composition 3: 50 g).
  • Composition 1 of Example Group 5 is the same as Composition 1 of Example Group 4; therefore, the results of using Composition 1 are not duplicated graphically in Figure 10.
  • Figure 10 shows that the operational window remains steady as lesser amounts of Paselli PGF pregel are employed until 75 g are used, upon which the operational window increases significantly. This shows that the pregelatinized starch supplied by the recycled material provides a substantial amount of the overall pregelatinized starch, since the effect of the Paselli PGF does not show a significant effect until an amount of 75 g is used.
  • Figure 10 illustrates the moderating effect on system reactivity ofthe increased amounts of fill weights, resulting in increased variability of allowable fill weights that yield high quality molded articles.
  • a starch based composition was provided having 30% pregelatinized starch and then tested using the molding apparatus and methods set forth above in Example Group
  • composition used in each case included the following components:
  • the concentration of guar gum is expressed as a percentage by weight ofthe total solids within the composition.
  • the results of the test runs conducted in Example Group 6 are set forth in Table 6 as follows:
  • Table 6 The data of Table 6 is graphically compiled in Figures 11 , which shows the operational window of acceptable fill weights as a function of top mold temperature for the above-identified composition.
  • the magnitude ofthe operational window increases as temperature is increased up to a maximum window at 205° C, then decreases very slightly at 215° C, which is a very large window at such a high mold temperature compared to what was attainable using prior art compositions.
  • Figure 12 shows the operational window of acceptable fill weights for a composition similar to the composition of Example Group 6, except that the water content is increased to 1500 g. Except for the discontinuity at 185° C, the data is similar to the data set forth in Figure 11 , such that increasing the mold temperature generally increases the operation window for fill weight.
  • Examnle Group 7 Compositions containing different types and/or amounts of pregelatinized starch were tested using the apparatus described in Example Group 2. The bottom mold temperature was held to between 190° C and 195° C, while the top mold temperature was held between 200° C and 205° C, although there naturally were unavailable fluctuations in mold temperature. Only the average mold temperature is set forth in Table 7. Each composition included 500 g calcium carbonate, 500 g total starch, 120 g fibers, 20 g magnesium stearate, and varying amounts of water between 1300-1500 g in 100 g intervals.
  • the pregelatinized starch component included either Paselli PGF starch (identified in Table 7 as "PGF") or Paselli P (identified in Table 7 as "P").
  • Paselli PGF and P are similar but differ in their functionality and gelating power. Whereas PGF was previously identified as having a gelating power of 2000 Brabender Units, P has a slightly lower gelating power of 1800 Brabender Units, compared to 1000 for gelatinized unmodified potato starch and 600 for gelatinized unmodified corn starch (Ultra Crisp).
  • PGF was previously identified as having a gelating power of 2000 Brabender Units
  • P has a slightly lower gelating power of 1800 Brabender Units, compared to 1000 for gelatinized unmodified potato starch and 600 for gelatinized unmodified corn starch (Ultra Crisp).
  • Figure 13 plots the operational window of acceptable fill weights as a function of water content for compositions that contain 100 g of Paselli PGF pregel.
  • Figure 13 shows that there is a remarkably large range of acceptable fill weights, especially for the compositions containing 1300 g water.
  • Figure 14 plots the operational window of acceptable fill weights as a function of water content for compositions that contain 100 g of Paselli P pregel.
  • Figure 14 shows that there is also a remarkably large range of acceptable fill weights for compositions that include 100 g Paselli P.
  • the operational window for fill weight decreased somewhat as the amount of water was increased, system reactivity was clearly moderated compared to prior art compositions using little or no pregelatinized starch.
  • Figure 15 plots the operational window of acceptable fill weights as a function of water content for compositions that contain 75 g of Paselli PGF pregel.
  • Figure 15 shows that there is a very large range of acceptable fill weights, especially for compositions include 1300 g or 1400 g water.
  • the operational window for fill weight decreased as the amount of water was increased, particularly at a water content of 1500 g.
  • the operational window associated with compositions containing 1500 g water is relatively large compared to results obtained using prior art compositions. This is especially true in light of the relatively small vent hole size ofthe molding apparatus (0.040").
  • Example Group 8 Starch-based compositions comprising water, an ungelatinized starch binder, and a gelatinized starch binder are provided as follows:
  • the concentration of pregelatinized starch has a low point of 12% by weight of the total starch content and for successive mixtures is increased in 2% intervals up to a maximum concentration of 50% by weight of total starch.
  • the water content is adjusted in order to maintain a viscosity of at least about 5,000 cps and is increased as the pregelatinized starch concentration is increased.
  • compositions demonstrate the important moderating effect of the pregelatinized starch component, although the beneficial effect is increased if fibers and inorganic fillers are also included. If only calcium carbonate is added to the above compositions, the bake time operational window is further increased, which demonstrates the importance of including an inorganic filler within the molding compositions ofthe present invention.
  • the present invention provides compositions and methods for manufacturing novel starch-bound materials that can replace thermoplastics and other conventional materials for producing packaging materials and other articles.
  • the present invention further provides compositions that allow for a higher water content without the negative effects of increased reactivity ofthe molding material during molding.
  • the present invention also provides compositions and methods for improving the dispersion of fibers or other fillers within starch-based materials without the need for using highly aqueous slurries with intolerably high reactivity, such as slurries used in the paper-,making industry.
  • compositions and methods allow for a more thorough dispersion of fibers, particularly relatively long-length fibers (i.e., those having an average length greater than about 2 mm) and/or fibers of high aspect ratio (i.e., at least about 25:1), within the starch-based compositions.
  • the present invention yet provides compositions that allow for inclusion of higher concentrations of inorganic fillers while maintaining adequately strong molded starch- bound articles.
  • the present invention further provides compositions and methods that make possible the manufacture of articles while increasing the window of allowable water concentrations, fill volumes, molding temperatures, and vent sizes.
  • the present invention yet provides compositions and methods that result in the ability to significantly reduce the thermal molding time while manufacturing articles that are of equal or greater quality compared to articles manufactured using the compositions and methods ofthe prior art. Furthermore, such compositions and methods yield hardened, starch-based articles that do not require the addition of synthetic polymers or prolonged, high- humidity conditioning in order to obtain the required flexibility, strength and toughness.
  • the present invention further provides compositions and methods that yield starch-bound articles that did not require the application of a coating or the inclusion of a synthetic polymer to maintain the proper moisture within the starch-bound articles.
  • the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrated and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Abstract

L'invention porte sur des compositions et les procédés permettant d'améliorer le rendement et la fiabilité d'un processus de moulage à chaud utilisé pour fabriquer des articles liés par de l'amidon possédant une matrice cellulaire structurale. L'introduction de quantités importantes d'amidon pré-gélifié dans la composition de moulage à base d'amidon accroît grandement la plage opérationnelle admissible pour diverses variables de composition et de traitement, par exemple, la teneur initiale en eau de la composition de moulage, la quantité (poids de remplissage) de composition placée dans le moule, la température de celui-ci et la taille du trou d'aération. On a vu qu'une quantité d'amidon pré-gélifié, comprise entre 12 et 50 % en poids de la teneur totale en amidon de la composition de moulage modère ou neutralise notablement la réactivité du système due, par exemple, à l'augmentation de la teneur en eau, au poids de remplissage, à la température du moule et à la taille du trou d'aération. Le solde d'amidon est constitué, dans la composition de moulage, de granules d'amidon non gélifié mais se gélifiant durant le processus de moulage à chaud. La composition de moulage comporte, de surcroît, des fibres, au rapport dimensionnel élevé, dispersées de manière sensiblement homogène, une matière de charge inorganique, un agent de démoulage et de l'eau.
PCT/US1996/020116 1995-12-22 1996-12-17 Compositions a base d'amidon WO1997023333A1 (fr)

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Cited By (6)

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Publication number Priority date Publication date Assignee Title
FR2777495A1 (fr) * 1998-04-21 1999-10-22 Itw Litec France Procede de fabrication en continu de profiles ou plaques, installation pour la mise en oeuvre du procede et produits ainsi obtenus
DE19950744A1 (de) * 1999-10-21 2001-04-26 Ulrich Tscheuschler Herstellung eines Verbundwerkstoffes durch Mischung von biologisch abbaubaren Polymeren mit Naturfasern
US6878199B2 (en) 2002-01-11 2005-04-12 New Ice Limited Biodegradable or compostable containers
US7235256B2 (en) 1998-10-30 2007-06-26 Rj Innovation Method of preventing parturient hypocalcemia in animals and compositions used therein
US8927622B2 (en) 2007-07-03 2015-01-06 Chamness Biodegradables, Llc Biodegradable and compostable composition having improved physical and chemical properties
WO2020254877A1 (fr) 2019-06-20 2020-12-24 Eps Global Marketing Ltd. Compositions de masse de moulage biodégradables, compostables, articles moulés et procédés de fabrication

Citations (1)

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US5376320A (en) * 1990-02-06 1994-12-27 Biopac Biologische Verpackungssysteme Gesellschaft M.B.H. Process of producing rottable thin-walled shaped bodies made of starch

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5376320A (en) * 1990-02-06 1994-12-27 Biopac Biologische Verpackungssysteme Gesellschaft M.B.H. Process of producing rottable thin-walled shaped bodies made of starch

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2777495A1 (fr) * 1998-04-21 1999-10-22 Itw Litec France Procede de fabrication en continu de profiles ou plaques, installation pour la mise en oeuvre du procede et produits ainsi obtenus
EP0951987A1 (fr) * 1998-04-21 1999-10-27 ITW Litec France Procéde pour la Fabrication des Plaques et Profiles
US6416606B1 (en) 1998-04-21 2002-07-09 Itw Litec France Continuous manufacturing process for sections or plates
US7235256B2 (en) 1998-10-30 2007-06-26 Rj Innovation Method of preventing parturient hypocalcemia in animals and compositions used therein
DE19950744A1 (de) * 1999-10-21 2001-04-26 Ulrich Tscheuschler Herstellung eines Verbundwerkstoffes durch Mischung von biologisch abbaubaren Polymeren mit Naturfasern
US6878199B2 (en) 2002-01-11 2005-04-12 New Ice Limited Biodegradable or compostable containers
US7083673B2 (en) 2002-01-11 2006-08-01 New Ice Limited Biodegradable or compostable containers
US7967904B2 (en) 2002-01-11 2011-06-28 New Ice Limited Biodegradable or compostable containers
US8927622B2 (en) 2007-07-03 2015-01-06 Chamness Biodegradables, Llc Biodegradable and compostable composition having improved physical and chemical properties
WO2020254877A1 (fr) 2019-06-20 2020-12-24 Eps Global Marketing Ltd. Compositions de masse de moulage biodégradables, compostables, articles moulés et procédés de fabrication
CN114269824A (zh) * 2019-06-20 2022-04-01 Eps全球营销有限公司 可生物降解可堆肥的模塑物料组合物、模塑制品和制造方法
CN114269824B (zh) * 2019-06-20 2024-02-20 Eps全球营销有限公司 可生物降解可堆肥的模塑物料组合物、模塑制品和制造方法

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